1 // SPDX-License-Identifier: GPL-2.0
2 #include <linux/compiler.h>
3 #include <linux/string.h>
4 #include <sys/types.h>
5 #include <sys/stat.h>
6 #include <unistd.h>
7 #include <string.h>
8 #include <stdlib.h>
9 #include <stdio.h>
10 #include "subcmd-util.h"
11 #include "exec-cmd.h"
12 #include "subcmd-config.h"
13 
14 #define MAX_ARGS	32
15 #define PATH_MAX	4096
16 
17 static const char *argv_exec_path;
18 static const char *argv0_path;
19 
exec_cmd_init(const char * exec_name,const char * prefix,const char * exec_path,const char * exec_path_env)20 void exec_cmd_init(const char *exec_name, const char *prefix,
21 		   const char *exec_path, const char *exec_path_env)
22 {
23 	subcmd_config.exec_name		= exec_name;
24 	subcmd_config.prefix		= prefix;
25 	subcmd_config.exec_path		= exec_path;
26 	subcmd_config.exec_path_env	= exec_path_env;
27 
28 	/* Setup environment variable for invoked shell script. */
29 	setenv("PREFIX", prefix, 1);
30 }
31 
32 #define is_dir_sep(c) ((c) == '/')
33 
is_absolute_path(const char * path)34 static int is_absolute_path(const char *path)
35 {
36 	return path[0] == '/';
37 }
38 
get_pwd_cwd(void)39 static const char *get_pwd_cwd(void)
40 {
41 	static char cwd[PATH_MAX + 1];
42 	char *pwd;
43 	struct stat cwd_stat, pwd_stat;
44 	if (getcwd(cwd, PATH_MAX) == NULL)
45 		return NULL;
46 	pwd = getenv("PWD");
47 	if (pwd && strcmp(pwd, cwd)) {
48 		stat(cwd, &cwd_stat);
49 		if (!stat(pwd, &pwd_stat) &&
50 		    pwd_stat.st_dev == cwd_stat.st_dev &&
51 		    pwd_stat.st_ino == cwd_stat.st_ino) {
52 			strlcpy(cwd, pwd, PATH_MAX);
53 		}
54 	}
55 	return cwd;
56 }
57 
make_nonrelative_path(const char * path)58 static const char *make_nonrelative_path(const char *path)
59 {
60 	static char buf[PATH_MAX + 1];
61 
62 	if (is_absolute_path(path)) {
63 		if (strlcpy(buf, path, PATH_MAX) >= PATH_MAX)
64 			die("Too long path: %.*s", 60, path);
65 	} else {
66 		const char *cwd = get_pwd_cwd();
67 		if (!cwd)
68 			die("Cannot determine the current working directory");
69 		if (snprintf(buf, PATH_MAX, "%s/%s", cwd, path) >= PATH_MAX)
70 			die("Too long path: %.*s", 60, path);
71 	}
72 	return buf;
73 }
74 
system_path(const char * path)75 char *system_path(const char *path)
76 {
77 	char *buf = NULL;
78 
79 	if (is_absolute_path(path))
80 		return strdup(path);
81 
82 	astrcatf(&buf, "%s/%s", subcmd_config.prefix, path);
83 
84 	return buf;
85 }
86 
extract_argv0_path(const char * argv0)87 const char *extract_argv0_path(const char *argv0)
88 {
89 	const char *slash;
90 
91 	if (!argv0 || !*argv0)
92 		return NULL;
93 	slash = argv0 + strlen(argv0);
94 
95 	while (argv0 <= slash && !is_dir_sep(*slash))
96 		slash--;
97 
98 	if (slash >= argv0) {
99 		argv0_path = strndup(argv0, slash - argv0);
100 		return argv0_path ? slash + 1 : NULL;
101 	}
102 
103 	return argv0;
104 }
105 
set_argv_exec_path(const char * exec_path)106 void set_argv_exec_path(const char *exec_path)
107 {
108 	argv_exec_path = exec_path;
109 	/*
110 	 * Propagate this setting to external programs.
111 	 */
112 	setenv(subcmd_config.exec_path_env, exec_path, 1);
113 }
114 
115 
116 /* Returns the highest-priority location to look for subprograms. */
get_argv_exec_path(void)117 char *get_argv_exec_path(void)
118 {
119 	char *env;
120 
121 	if (argv_exec_path)
122 		return strdup(argv_exec_path);
123 
124 	env = getenv(subcmd_config.exec_path_env);
125 	if (env && *env)
126 		return strdup(env);
127 
128 	return system_path(subcmd_config.exec_path);
129 }
130 
add_path(char ** out,const char * path)131 static void add_path(char **out, const char *path)
132 {
133 	if (path && *path) {
134 		if (is_absolute_path(path))
135 			astrcat(out, path);
136 		else
137 			astrcat(out, make_nonrelative_path(path));
138 
139 		astrcat(out, ":");
140 	}
141 }
142 
setup_path(void)143 void setup_path(void)
144 {
145 	const char *old_path = getenv("PATH");
146 	char *new_path = NULL;
147 	char *tmp = get_argv_exec_path();
148 
149 	add_path(&new_path, tmp);
150 	add_path(&new_path, argv0_path);
151 	free(tmp);
152 
153 	if (old_path)
154 		astrcat(&new_path, old_path);
155 	else
156 		astrcat(&new_path, "/usr/local/bin:/usr/bin:/bin");
157 
158 	setenv("PATH", new_path, 1);
159 
160 	free(new_path);
161 }
162 
prepare_exec_cmd(const char ** argv)163 static const char **prepare_exec_cmd(const char **argv)
164 {
165 	int argc;
166 	const char **nargv;
167 
168 	for (argc = 0; argv[argc]; argc++)
169 		; /* just counting */
170 	nargv = malloc(sizeof(*nargv) * (argc + 2));
171 
172 	nargv[0] = subcmd_config.exec_name;
173 	for (argc = 0; argv[argc]; argc++)
174 		nargv[argc + 1] = argv[argc];
175 	nargv[argc + 1] = NULL;
176 	return nargv;
177 }
178 
execv_cmd(const char ** argv)179 int execv_cmd(const char **argv) {
180 	const char **nargv = prepare_exec_cmd(argv);
181 
182 	/* execvp() can only ever return if it fails */
183 	execvp(subcmd_config.exec_name, (char **)nargv);
184 
185 	free(nargv);
186 	return -1;
187 }
188 
189 
execl_cmd(const char * cmd,...)190 int execl_cmd(const char *cmd,...)
191 {
192 	int argc;
193 	const char *argv[MAX_ARGS + 1];
194 	const char *arg;
195 	va_list param;
196 
197 	va_start(param, cmd);
198 	argv[0] = cmd;
199 	argc = 1;
200 	while (argc < MAX_ARGS) {
201 		arg = argv[argc++] = va_arg(param, char *);
202 		if (!arg)
203 			break;
204 	}
205 	va_end(param);
206 	if (MAX_ARGS <= argc) {
207 		fprintf(stderr, " Error: too many args to run %s\n", cmd);
208 		return -1;
209 	}
210 
211 	argv[argc] = NULL;
212 	return execv_cmd(argv);
213 }
214